Oil formulations supply nutrients to the skin and provide gloss and moisturizing power to the skin, but they lack fresh moisturizing content and are inconvenient to use because they flow down when drawn off into a hand and applied to the face due to low viscosity. In recent years, to overcome these inconveniences of customers, extensive studies have been conducted on oil-in-water type (O/W) emulsions containing moisturizing content by stabilizing high contents of oil-soluble components by manufacturers.
The easiest stabilization of the high contents of oil-soluble components is to increase the viscosity of water phase using a carbopol-based or acryl-based thickening agent together with a surfactant. However, an O/W emulsion manufactured by these methods is not distinguished from a conventional lotion or cream formulation in terms of formulation, and also there is a problem that it is difficult to exhibit inherent feelings of use and properties of the oil-soluble components.
For these reasons, it is the latest trend that the manufacturers are studying methods for manufacturing a transparent gel in which a high content of oil-soluble components stabilized by making the oil-soluble components into small particles in a size of 200 nm or less by using a high-pressure emulsification method. The gel thus manufactured has a transparency and high viscosity as the particles of the oil-soluble components are small, and little or no thickening agent can be used. Thus, when it is applied, it exhibits a formulation similar to a moisture gel in the initial stage, and when it is rolled on the skin, the gel structure is easily collapsed to give a high moisture content, but at the end, it not only leaves a film of oil-soluble components on the skin, but also allows the soluble components.
In order to make small particles of 200 nm or less using such a high-pressure emulsification method and to manufacture a transparent gel, is common to make the particle size of the oil-soluble components small together with a polyglyceryl-based surfactant or to use a polyethylene-based (PEG) surfactant or an ionic surfactant for stabilizing an interface film together. However, when the PEG-based surfactant or ionic surfactant is used, there is a safety concern that it causes skin irritation. Nevertheless, the reason for using a PEG-based surfactant or an ionic surfactant in general because it is difficult to reduce the particle size of a nano-emulsion containing a high-content of oil-soluble components or to stabilize an interface film if the use of these surfactants is excluded. Thus, it would be difficult to realize the transparency characteristic of the solubilized gel formulation, and to guarantee the product quality for a long time in various environments (low temperature, high temperature, etc.) in which customers use the product.